1. Technical Field
This invention relates to an optical device and a projector.
2. Related Art
Recently, there has been an image display device using a light modulation element in which light emitted from a light source is cast to a light modulation element such as a liquid crystal panel, the incident light is modulated by the light modulation element, and then the modulated light is projected onto a screen. In such an image display device, the light except for the light projected onto the screen is absorbed by the light modulation element and its peripheral optical elements, generating heat. Thus, a device having a cooler using a gas for radiating the generated heat has been proposed. However, as the density of semiconductors becomes higher, the calorific value per unit volume increases and the cooling with a gas cannot realize sufficient radiation. Therefore, cooling devices using a liquid have been proposed, as disclosed in JP-A-2003-195253, JP-A-2005-227353 and JP-A-2002-131737.
In the projector disclosed in JP-A-2003-195253, a polarizer is cooled by using ethyleneglycol as a refrigerant. Specifically, the heat generated from the polarizer is transmitted to a refrigerant filling a refrigerant-filled part and the refrigerant heated by the heat rises because of the lowered density, causing free convection within the refrigerant. The heat transferred by this convection performs heat exchange with external air, thereby cooling the polarizer.
The projector disclosed in JP-A-2005-227353 has a fluid circulation member through which a refrigerant flows. A cooled fluid is sent to the fluid circulation member from a main tank and this cooling fluid is branched and thus sent into three light modulation element holding bodies by a fluid branching unit. This causes the heat generated from a liquid crystal panel and a polarizer to be transmitted to the cooled fluid in the fluid circulation member. Then heated cooling fluid is sent to a radiator, and when passing through a tubular member of the radiator, the cooling fluid is transmitted to a radiation fin and gets cooled.
In the projector disclosed in JP-A-2002-131737, a liquid crystal panel for red light, a liquid crystal panel for green light, a liquid crystal panel for blue light, and their respective light incident-side polarizers and light exiting-side polarizers are arranged within a rectangular box-shaped cooling container. A refrigerant is sealed in this cooling container, and as this refrigerant is forcedly circulated by a stirring unit the refrigerant absorbs the heat generated from a polarization element and a liquid crystal panel. The heat absorbed by the refrigerant moves to the inner wall surface of the cooling container and performs heat exchanges with external air by using a cooling fin provided on the outer surface of the cooling container.
The above techniques have the following problems. That is, in the projector disclosed in JP-A-2003-195253, since the polarizer is cooled by using free convection, it is difficult to sufficiently cool the polarizer.
In the projector disclosed in JP-A-2005-227353, since plural fluid circulation members are used for cooling the light modulation element, the configuration is complicated by the connection of these members. Also, the refrigerant may leak from the connecting parts of the fluid circulation n embers and dust may enter the fluid circulation members because of the connection of the fluid circulation members.
In the liquid display device disclosed in JP-A-2002-131737, since an entire liquid crystal display unit is immersed in a refrigerant, the refrigerant may enter the liquid crystal panel. Also, since three liquid crystal panels are arranged within one cooling container, assembly of the liquid crystal display device is difficult. Maintenance is difficult when one of the liquid crystal panels has trouble, and the other liquid crystal panels may also have trouble.